# Multiple choice question for engineering

## Set 1

1. Which of the following is not a type of arc welding?

a) Plasma

b) Electro-slag

c) Submerged

d) Air-acetylene

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2. Which of the following is not a type of resistance welding?

a) Seam

b) Projection

c) Electro-slag

d) Spot

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3. Which of the following materials are not suited for cold welding?

a) Brass

b) Steel

c) Silver

d) Gold

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4. What is the cross-sectional shape of a thermoplastic welding rod?

a) Triangular

b) Hexagonal

c) Square

d) Pentagonal

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5. Which of the following is not a type of related processes?

a) Soldering

b) Percussion

c) Brazing

d) Hard-pressing

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6. Laser is classified under newer beam.

a) True

b) False

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7. Which of the following is not a type of solid state welding?

a) Projection

b) Ultrasonic

c) Friction

d) Diffusion

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8. What is the density of the plastic used in speed tip welding?

a) 916 kg/m^{3}

b) 923 kg/m^{3}

c) 946 kg/m^{3}

d) 982 kg/m^{3}

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^{3}and it starts melting at 130°C.

9. Which of the following could be considered as a related process?

a) Explosive

b) Oxy-Hydrogen welding

c) Oxy-Acetylene cutting

d) Electron-beam

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10. A liquid phase has to be used in cold welding.

a) True

b) False

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## Set 2

1. What is the capacity of automatic welding machine?

a) 100 to 200A

b) 300 to 400A

c) 500 to 700A

d) 800 to 3000A

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2. What is the capacity of a light manual welding machine?

a) 100 to 200A

b) 300 to 400A

c) 500 to 700A

d) 800 to 3000A

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3. What is the current required in an Oxygen’s INDARC 400 (S) transformer?

a) 20 amp to 100 amp

b) 40 amp to 250 amp

c) 50 amp to 400 amp

d) 60 amp to 500 amp

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4. What is the efficiency of an A.C. welding transformer?

a) 0.6

b) 0.7

c) 0.8

d) 0.9

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5. What is the amount of electric energy required per kg in dc welding operation?

a) 1-4 kWh

b) 3-7 kWh

c) 4-9 kWh

d) 6-10 kWh

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6. Which material is not used for making non-consumable electrodes?

a) Carbon

b) Graphite

c) Sodium

d) Tungsten

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7. Which of the following characteristic does not define a coated electrode?

a) Maintenance of arc

b) Protection from oxygen

c) Protection from nitrogen

d) Preventing other elements into molten metal

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8. What is the amount of carbon contained by a soft steel wire?

a) 0.1% to 0.18%

b) 0.15% to 0.22%

c) 0.18% to 0.26%

d) 0.2% to 0.27%

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9. What is the percentage of carbon present in low alloy steel?

a) 0.15%

b) 0.2%

c) 0.25%

d) 0.3%

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10. The presence of arc blower makes good quality welds.

a) True

b) False

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## Set 3

1. Which of the following methods cannot be used for welding carbon steel?

a) Arc welding

b) Gas welding

c) Ultrasonic welding

d) Forge welding

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2. High alloys steels are preheated up to what temperature?

a) 350°C

b) 400°C

c) 450°C

d) 500°C

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3. Up to what percent of carbon content in steel, it is not required to preheat it?

a) 0.25% – 0.3%

b) 0.3% – 0.35%

c) 0.35% – 0.4%

d) 0.4% – 0.45%

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4. Which of the following material is not used in alloy steels?

a) Molybdenum

b) Nickel

c) Chromium

d) Sodium

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5. Which among the following methods is best suited for stainless steels?

a) Electric butt welding

b) Seam welding

c) Flux coated arc welding

d) Oxy-hydrogen welding

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6. Stainless steels are annealed at what temperature?

a) 650°C – 700°C

b) 700°C – 750°C

c) 750°C – 800°C

d) 800°C – 850°C

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7. Which of the following is not a material used for making an electrode in metal arc welding, for treating stainless steels?

a) Niobium

b) Columbium

c) Titanium

d) Potassium

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8. What is the temperature needed for preheating in cast irons?

a) 550°C

b) 600°C

c) 650°C

d) 700°C

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9. Low carbon steels need not be preheated before welding.

a) True

b) False

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10. Carbon steels can be fusion welded.

a) True

b) False

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## Set 4

1. The point form of Gauss law is given by, Div(V) = ρv

State True/False.

a) True

b) False

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2. If a function is said to be harmonic, then

a) Curl(Grad V) = 0

b) Div(Curl V) = 0

c) Div(Grad V) = 0

d) Grad(Curl V) = 0

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3. The Poisson equation cannot be determined from Laplace equation. State True/False.

a) True

b) False

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4. Given the potential V = 25 sin θ, in free space, determine whether V satisfies Laplace’s equation.

a) Yes

b) No

c) Data sufficient

d) Potential is not defined

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^{2}V = 0 (Del)

^{2}V = (Del)

^{2}(25 sin θ), which is not equal to zero. Thus the field does not satisfy Laplace equation.

5. If a potential V is 2V at x = 1mm and is zero at x=0 and volume charge density is -106εo, constant throughout the free space region between x = 0 and x = 1mm. Calculate V at x = 0.5mm.

a) 0.875

b) 0.675

c) 0.475

d) 0.275

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^{2}(V) = -ρv/εo= +106 On integrating twice with respect to x, V = 106. (x

^{2}/2) + C1x + C2. Substitute the boundary conditions, x = 0, V = 0 and x = 1mm, V = 2V in V, C1 = 1500 and C2 = 0. At x = 0.5mm, we get, V = 0.875V.

6. Find the Laplace equation value of the following potential field

V = x^{2} – y^{2} + z^{2}

a) 0

b) 2

c) 4

d) 6

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7. Find the Laplace equation value of the following potential field

V = ρ cosφ + z

a) 0

b) 1

c) 2

d) 3

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^{2}(ρ cosφ + z)= (cos φ/r) – (cos φ/r) + 0 = 0, this satisfies Laplace equation. The value is 0.

8. Find the Laplace equation value of the following potential field

V = r cos θ + φ

a) 3

b) 2

c) 1

d) 0

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^{2}(r cos θ + φ) = (2 cosθ/r) – (2 cosθ/r) + 0 = 0, this satisfies Laplace equation. This value is 0.

9. The Laplacian operator cannot be used in which one the following?

a) Two dimensional heat equation

b) Two dimensional wave equation

c) Poisson equation

d) Maxwell equation

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10. When a potential satisfies Laplace equation, then it is said to be

a) Solenoidal

b) Divergent

c) Lamellar

d) Harmonic

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## Set 5

1. Find the conductivity of a material with conduction current density 100 units and electric field of 4 units.

a) 25

b) 400

c) 0.04

d) 1600

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2. Calculate the displacement current density when the electric flux density is 20sin 0.5t.

a) 10sin 0.5t

b) 10cos 0.5t

c) 20sin 2t

d) 20cos 2t

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3. Find the magnitude of the displacement current density in air at a frequency of 18GHz in frequency domain. Take electric field E as 4 units.

a) 18

b) 72

c) 36

d) 4

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4. Calculate the frequency at which the conduction and displacement currents become equal with unity conductivity in a material of permittivity 2.

a) 18 GHz

b) 9 GHz

c) 36 GHz

d) 24 GHz

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5. The ratio of conduction to displacement current density is referred to as

a) Attenuation constant

b) Propagation constant

c) Loss tangent

d) Dielectric constant

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6. If the loss tangent is very less, then the material will be a

a) Conductor

b) Lossless dielectric

c) Lossy dielectric

d) Insulator

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7. In good conductors, the electric and magnetic fields will be

a) 45 in phase

b) 45 out of phase

c) 90 in phase

d) 90 out of phase

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8. In free space, which of the following will be zero?

a) Permittivity

b) Permeability

c) Conductivity

d) Resistivity

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9. If the intrinsic angle is 20, then find the loss tangent.

a) tan 20

b) tan 40

c) tan 60

d) tan 80

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10. The intrinsic impedance of free space is given by

a) 272 ohm

b) 412 ohm

c) 740 ohm

d) 377 ohm

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^{-12}and μo = 4π x 10

^{-7}. On substituting the values, we get η = 377 ohm.